GB2211893A

GB2211893A - Hydraulic gear machine (pump or motor)

Info

Publication number: GB2211893A
Application number: GB8825755A
Authority: GB
Inventors: Gerhard Nonnenmacher
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1987-11-04
Filing date: 1988-11-03
Publication date: 1989-07-12
Anticipated expiration: 2008-11-03
Also published as: GB2211893B; GB8825755D0; DE3737403C2; DE3737403A1; IT8822089V0; IT215412Z2

Description

2211893 Hydraulic gear machine (pump or motor)

Prior art

The invention starts from a gear machine accord ing to the p.e-characterizing clause of the main claim.

The delivery volume of such gear machines becomes greater as the ratio of wheel diameter to distance between axes is made greater. A tooth system with the highest possible teeth is therefore required. With the customary evolute toothed and cycloidal. toothed wheels, this requirement can only be met by a greatly reduced number of teeth. This in turn causes high pulsation and intense noise.

Advantage of the invention Compared to the above, the gear machine according to the invention having the characterizing features of the main claim possesses the advantage that they permit wheels of great tooth height whilst maintaining the greatest possible number of teeth, so as to restrict pulsation and noise as described above. The outlay to achieve this is no greater than with gear machines known previously. It also has the advantage that the ratio of delivery volume to structural volume is definitely improved whilst maintaining a favourable number of teeth. It is also possible to reduce the flank pressure in the critical range. so that the useful life of the wheels is prolonged.

Further advantages and improvements of the gear machine according to the invention will be apparent from the subordinate claims.

D r a w i n g Fig. 1 shows partially the two gears of a gear m a c h i n e, Fig. 2 to 4 relate to diagrammatic views.

- 2 Description of the exemplary embodiment

In Fig. 1, 10 and 11 designate the two gears of an otherwise customary gear machine, the construction of which is not discussed in detail, because housing and bearing means of the wheels are not relevant to the invention and because they are also already known. W designates the pitch point of the gears, E the line of action. In known gear machines this forms a straight line, gen- erally at an angle of action of approximately 200. The gear machine according to the invention has a totally different line of action, namely such that a nonevolute and noncycloidal tooth system is obtained. The line of action here forms a curve symmetrical in rotation relative to the pitch point. In the region of the pitch point W the tangent of the line of action exhibits a relatively small angle, conveniently between 4 and 150, optimally approximately 60. The line of action is also characterized in that the angle of action-starting from the pitch point W - increases continually, particularly steadily, as in the exemplary embodiment according to Fig. 1, but it may also be an Archimedean or logarithmic spiral (Fig. 2) starting from the wheel centre, consist of two circles with tangent T (Fig. 3) or be constructed according to a specific mathematical formula, as illustrated in Fig. 4.

The formula reads: y = -a arc sinbx + cx, where for example a = 7.5, b = 0.15, c = 1.

The increase in the angle of action should be kept so slight that the undercut at the tooth flank just does not reduce the overlap to values beiow 1, that is to say that the converse does not become smaller than 1. This dimensioning achieves the maximum possible tooth height for a given number of teeth.

Claims

3 C 1 a i m s

1. Hydraulic gear machine (pump or motor) having gears meshing in external action with nonevolute and non- cycloidal tooth system, characterized by the following features:

a) The angle of action of the line of action (E) of the gears and the pitch point (W) is very small; b) The line of action forms a curve extending symmetrically in rotation to the pitch point so that the angle of action increases with increasing distance of the line of action from the pitch point; c) The increase in the angle of action along the line of action must be chosen at least large enough for the action overlap not to become smaller than 1.

2. Machine according to Claim 1, characterized in that the angle of action of the line of action at the pitch point is between 40 and 150, preferably 60.

3. Machine according to Claim 1 andlor 2, charac terized in that the angle of action of the line of action increases steadily with increasing distance from the pitch p o i n t.

4. A hydraulic gear machine substantially as herein described with reference to the accompanying drawings.

Published 1989 atThePatelit Office, State House, 6671 High Holborn, UndonWC1R4TP.Ftrther copies 2naybe obtained from ThePatentof[lce. Sales Branch, St Maxy Cray, Oil)lngtoii, Kent BRS 3RD. Printed by Multiplex techniques ltd, St Mary Cray. Kent. Con. 1187

4. Machine according to Claim 1 or 2, characterized in that the line of action consists of two spirals about the wheel centre which meet symmetrically in rotation at the pitch point.

5. Machine according to Claim 1 and/or 2, charac terized in that the line of action extends according to a specific mathematical formula according to the exemplary embodiment of Fig. 3.

6. Machine according to Claim 1 and/or 2, charac terized in that the line of action is composed of two circles with tangents at the pitch point.

7. A hydraulic gear machine substantially as herein described with reference to the accompanying drawings.

7 Amendments to the claims have been filed as follows Hydraulic gear machine (pump or moto.r) having gears meshing in external action with nonevolute and non-cycloidal tooth system in which the line of action is a curve extending point-symmetrically to the pitch point so that the angle of action increases with increasing distance of the line of action from the pitch point and the contact ratio is greater than 1, characterized in that the angle of action of the line of action (E) at the pitch point (W) is between 40 and 100.

2. Machine according to Claim 1, characterized in that the line of action consists of two spirals about the wheel centre which meet point-symmetrically at the pitch point.

3. Machine according to Claim 1, characterized in that the line of action consists of two circular arcs which meet point- symmetrically at the pitch point.